February 11th lecture Flashcards
What is the Albedo Feedback loop?
- Melting of sea ice leads to….
- Lowered Albedo leads to….
- Increased absorption of sunlight leads to…..
How does increasing the salinity of sea water alter the freezing point?
The higher the salinity the lowers the freezing point.
What temperature does normal salinity level sea water freeze at?
-1.8C
What is Brine rejection?
It is the process of salt being squeezed into the water belowt due to the surface layer of ice being frozen
What does brine rejection lead to? ( three main points )
Brine rejection leads to a higher salinity and thus denser water underneath the newly formed ice, leading to this water sinking and mixing with the water masses below.
The increased salinity also leads to the water below the ice having its freezing temperature being lowered
What are the seven stages of ice development?
- frazial ice
- grease ice
- pancake ice
- Nilas
- young ice
- first year ice
- Old ice
What is Frazial ice?
small spicules and platelets freely suspended in the water coloum
What is grease ice?
After the Frazial ice stage when the ice particles have coagulated to form a soupy later on the surface.
What are the charicteristics of grease ice?
reflects little light
give the surface a matt appearance
How does grease ice behave?
behaves in a
viscous fluid-like manner, and does not form distinct
ice floes
What is pancake ice?
Circular peaces of ice from 30cm - 3m in diameter, and up to 10cm in thickness with a raised rim due to collisions with other pancake ice patches
How do ice sheet increase in thickness?
Once a sheet of ice has formed, it can increase in thickness
by the freezing of water on its lower surface.
How can the water below the ice surface freeze?
When the air above the ice is colder than the water below the
ice, heat is removed by conduction through the ice from the
water to the air above
The rate at which heat flows from the water is?
Proportional to the temperature difference between air an water
and is inversely proportional to the thickness of the ice layer and the snow cover on top of the ice.
How does young ice form?
• Forms under quiet conditions
How thick are dark nilas?
less than 5cm thick
How thick are Light nilas?
5-10cm thick
How thick is grey ice?
10 - 15cm thick
What is finger rafting?
when ice breaks almost like a pumkins smile
What is first year ice?
- 30cm thick
- can be up to 2.0m thick or thicker
- Associated with not more than 1 winter’s growth
What are gaps between ice floats called ?
fractures or
leads
What is multi year ice?
old ice that has survived at least 1 summers melt
What happens to the salt conentration in ice as it gets older?
The salt concentration gets smaller
As ice gets thicker and less dense what happens to it?
It starts to stand more and more out of the ocean
How thick is multi year ice?
6-7+ m thick
What is the radar backscatter and microwave emissivity of multi year ice? Why?
Due to its lower salinity, has higher radar backscatter and lower microwave emissivity
due to this we can see it from satellites easily
what does satillite data show about Multi year ice
There is less and less of it every year, and it is thinning
What are polynyas?
sections of open water during winter due to a broken ice sheet
How do polynyas occur?
A polynya forms when winds push the ice away from the coast or fast ice, resulting in the recurrent presence of open water even during winter.
Why are plolynyas importnat?
They allow marine life in the polar region to surface and have have sunlight
What is a iceburg
An Iceberg is a massive piece of ice of greatly varying shape, which has broken away from a glacier or ice shelf and which may be afloat or aground
are glaciers fresh or salt water?
Since they come from glacial ice, i.e.
snow, they are fresh
How are iceburgs controlled?
by water currents mainly
Does wind affect glacier movement?
Winds become more important to icebergs having high sail to draft ratio
or high ratio between the above water to below water portion
